Piston vacuum pump



FIG. 1 is a perspective view of the piston vacuum pump showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a front end elevational view thereof;

FIG. 5 is a rear end elevational view thereof;

FIG. 6 is a left side elevational view thereof; and

FIG. 7 is a right side elevational view thereof. 

The ornamental design for piston vacuum pump, as shown. 